WASHINGTON — The future of coal-fired power may lie in still-developing technology to capture the carbon dioxide it produces and put it to work in the oil field, Energy Secretary Ernest Moniz says.

In an interview with “Platts Energy Week,” Moniz talked up the potential not just for capturing and storing carbon dioxide produced by burning fossil fuels but for using more of it to glean oil from aging fields. Oil and gas companies already use the method — called enhanced oil recovery — around the United States, but Moniz sees it increasing.

“We're producing about 300,000 barrels per day using carbon dioxide to enhance oil recovery from older fields,” Moniz told the energy news show. “The estimates are that could increase by a factor of 10 to about 3 million barrels a day.”

But that would require a lot more carbon dioxide: about 600 million tons per year. “We could only get that by capturing it from industrial sources, power plants,” Moniz said.

The Energy Department is working to accelerate some enhanced oil recovery technology and operations. For instance, it has provided $431 million toward a project at Valero's refinery in Port Arthur, where carbon dioxide is being extracted from two steam methane devices, then dried, compressed and shipped to the West Hastings oil field 20 miles south of Houston.

Pumping the greenhouse gas underground has two benefits: It helps pull more crude out of the site, and it stores the carbon dioxide indefinitely.

The Port Arthur project involves just 1 million metric tons of carbon dioxide a year, which puts the potential scale of future efforts in perspective.

But carbon capture technology is still a long way from being commercially viable. The Port Arthur project notwithstanding, larger, utility-scale operations have proved challenging and expensive.

For example, costs have climbed for Southern Co.'s bid to build a plant in Mississippi with the goal of capturing and storing carbon dioxide emissions from the coal used at the facility.

The Energy Department is expected to play a major role in helping develop and commercialize the technology.

Moniz said the department's role includes “establishing for the longer term the science, the technology and the regulatory basis for large-scale capture of CO
{-2} and utilization and sequestration of that carbon dioxide.”

Carbon capture technology is seen as key to winnowing the greenhouse gas released by coal-fired power and helping to keep that energy source viable as the United States and other countries clamp down on emissions.

“We are trying to prepare the future of coal in a carbon-constrained world,” Moniz said.

President Barack Obama last week directed the Environmental Protection Agency to propose greenhouse gas emissions limits for new and existing power plants. A previous draft proposal that focused on new plants — along with the relatively low price of natural gas — prompted some companies to cancel plans to build new coal-fired facilities.

Moniz told Platts he expects coal to remain a “substantial” part of the U.S. energy mix. But he expects that more power plants will switch to natural gas from coal, based largely on cost considerations.

“There have been a bunch of coal plants that have closed. That's been market forces. It goes back to natural gas availability at low prices,” Moniz said. “What's been happening in the power sector over the past few years has been market-driven.”